Fluorescence chemosensing

Pei and coworkers [362] synthesized fluorene copolymer functionalized with imidazole ligands in the side chains (270). The PL emission of 270 was sensitive to the presence of metal cations in solution (particularly efficient quenching was due to Cu2+), which makes it a promising material for fluorescent chemosensing. 

Isgor YG, Akkaya EU (1997) Chemosensing in deep red a squaraine-based fluorescent chemosensor for pH. Tetrahedron Lett 38 7417-7420... 

The signal transduction is obviously a very important aspect of the chemosensing scheme. Even if one exciton could sample an almost infinite number of binding sites, that would be of no benefit if the analyte was not able to alter its fluorescence. In other words, in order for there to be ampHfication, a signal must be present that can be amplified. There are several mechanisms by which signal... 

From these expressions, it becomes clear that operating the chemosensing CP film near its lasing threshold will yield enhancements in fluorescence quenching, thereby enhancing sensitivity. Inspection of Fig. 5.9 shows that optimal sensitivity, at practical pump powers, is obtained when the pump power of the CP is at the onset of amplified stimulated emission (ASE), for the exposed film. Practical implementation of the concept would require rastering of the incident power intensity to locate the pump power that yields the maximum signal response. 

Fig. 5.21. Schematic diagram showing a cross-sectional view of a chemosensing bi-layer heteroj unction operating both before and after the presence of analyte. Amplified fluorescent polymer (AFP) is deposited on top of a charge transport layer (CTL) to form the heterojunction...

Fig. 7 Titration of the chemosensing ensemble [8 + 9] with some inorganic anions. HCO3 is able to displace the indicator from cape 8. an event signaled by fluorescence revival of the released indicator 9 (full triangles). Other anions do not displace the indicator and do not make fluorescence revive phosphate (open triangles) acetate (full circles) and sulfate (open diamonds).

Fig. PO The chemosensing ensemble paradigm. A fluorescent indicator occupies the cavity of a receptor, and its emission is quenched. When displaced by an analyte showing a higher affinity for the receptor, it displays its full fluorescence, so signaling the occun ence of analyte recognition.

Dinuclear silver complexes are instead much more represented, and some examples have been already mentioned and discussed in Section 3.2 (Fig. 11) for their chemosensing behavior other species are reported in Fig. 39. In particular, Liu and coworkers synthesized complexes of type 111-113, which resulted to display a fluorescent emission around 350 nm, generally associated with metal perturbed intrahgand processes though the authors reported that the intensity of this band appears weaker than that of... 

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